According to recent developments of information and communication apparatus, a semiconductor device such as a DRAM (Dynamic Random Access Memory) has required higher integration and higher accumulation for semiconductor elements (hereafter referred as an element) therein. Then, as an element has been further fined, various problems have also occurred. One of the problems on a DRAM is reduction of a storage capacitance. Because the capacitance of an element is proportional to its area, if the shape of an element was made smaller simply, the capacitance decreases in proportion to the square of a machining dimension. In case that a storage capacitance of a DRAM decreases, power consumption increases and reliability deteriorates since the refreshing is frequently required for compensating disappearance of electric charges. Therefore, even if an element is fined, it is necessary to keep a storage capacitance at a certain or higher level. Up to a 16-Mbit DRAM, the reduction of the capacitance owing to the fining of an element is compensated by making an oxide film forming a capacitor thin, and then the oxide film thickness is approximately 10 nm at present. However, because the thickness of the capacitor insulation film almost reaches the limit, materials having higher dielectric constant has been developed as a capacitor insulation film for a high integration memory of 64-Mbit or more. Then, tantalum oxide (Ta2O5) is studied for 64 to 256-Mbit, and barium strontium titanate ((Ba, Sr)TiO3:BST) and Pb zirconate titanate (Pb(Zr, Ti)O3:PZT) are studied for a 1-Gbit DRAM.
Furthermore, it is necessary to pay attention to selection of an electrode material in the development of the materials configuring the capacitor insulation film. The reason is that when forming a BST or PZT film on a conventionally-used Si electrode, the electrode film is oxidized, and a dielectric film other than the BST or PZT film is formed since a BST and PZT film require high temperature and oxidation atmosphere for forming them. The insulation film formed by oxidation of an electrode film causes a problem that a designed capacitance cannot be secured. Therefore, noble metals such as platinum (Pt), ruthenium (Ru), iridium (Ir), and palladium (Pd), or ruthenium oxide superior in oxidation resistance and heat resistance are studied as materials capable of withstanding various atmospheres for forming a BST and PZT film. Moreover, since PZT is used as a capacitor insulation film not only for a DRAM but also for a FRAM (Ferroelectric Random Access Memory), Pt, Ru, Ir, Pd, RuO2, and IrO2 are studied as electrode materials.
A throughput required for a semiconductor device has been severer year by year and thus, a signal delay is a problem for a device using wiring in which aluminum (Al) is used for a main conductive film. As an alternative wiring conductor to the Al wiring conductor, a wiring conductor which includes copper (Cu) having a lower electric resistance than that of Al as a main conductive film is studied. However, Cu may diffuse in a silicon oxide and thus, may deteriorate performances of a transistor.
Therefore, a barrier metal is necessary to prevent Cu from diffusing, and refractory metals such as TiN, tungsten (W), and tantalum (Ta) are studied as the barrier metal, as described in, for example, NIKKEI MICRODEVICE (pages 74 to 77 on the June issue in 1992).
Wiring using copper (Cu) for a main conductive film (hereafter referred as Cu wiring) as described in the above denotes a wiring film including the copper (Cu) element of which content is higher than contents of the other included elements.